# [Haskell-cafe] newbie question how to pass data

Mujtaba Boori mujtaba.boori at gmail.com
Tue Apr 20 00:45:31 EDT 2010

```Thanks Dan. Great help

but my problem has not solved yet
This doesn't work for type ((Float -> Float)->Bool)

to make it easier ignore the rotation and suppose I want just multiplay with
whatever (x ,y) and return the result to this type ((Float -> Float)->Bool)

note this type is shorten and replace by t
Type Point = (Float, Float)
Type Bitmap = Point -> Bool

so the function type actually
func :: Bitmap -> Float -> Bitmap

I want to take Bitmap do some calculation on Bitmap  the return it
as Bitmap.

GHCi response for Dan method is this
Couldn't match expected type `Bitmap'
against inferred type `(a, b)'
so it is missing a Bool.

hopefully it is clear .

On Mon, Apr 19, 2010 at 7:02 PM, Dan Weston <westondan at imageworks.com>wrote:

> First of all, your function

>
> func  (x,y) s dg  =((x*(cos dg) - y*(sin dg)),(x*(sin dg) - y*(cos dg)))
> does NOT work for type (Float -> Float), unless you mean that that is the
> type of the unused parameter s. Also, your desired type ((Float -> Float) ->
> Bool) itself looks suspicious. It must accept any function (without
> something to apply it to) and arbitrarily return True or False. How will you
> decide which? I suspect you need another parameter for this function.
>
> Second, on the off chance you are trying to calculate the position on a
> circle scaled then rotated an angle dg from (x,y), that new position is
>
> f (x,y) s dg = (s*(x*(cos dg) - y*(sin dg)),s*(x*(sin dg) + y*(cos dg)))
>
> in which case you are missing the s and the last minus sign in your formula
> should be a plus sign.
> If so, this can be evaluated with greater clarity (and probably accuracy)
> in polar coordinates:
>
> g (x,y) s dg = (r * cos a, r * sin a)
>  where r  = s * sqrt (x^2 + y^2)
>           a  = atan2 y x + dg
>
> Third, if you did not need the scale, I would use an underscore to make
> that clear:
>
> h (x,y) _ dg = (r * cos a, r * sin a)
>  where r  = sqrt (x^2 + y^2)
>           a  = atan2 y x + dg
>
> That's all the observations I can make unless you describe the problem more
> clearly. Sorry.
>
> Dan
>
> Mujtaba Boori wrote:
>
>> sorry
>> ok I am trying to make these calculation
>> func  (x,y) s dg  =((x*(cos dg) - y*(sin dg)),(x*(sin dg) - y*(cos dg)))
>>
>> This work for type (Float -> Float)
>>
>> but how can make it work with ((Float -> Float) -> Bool)
>>
>> because my main function that I want use with.  it takes (Float,Float)
>> ->Bool)  I need to return the same type ((Float,Float) ->Bool)  so it could
>> be used with other function.
>>
>> On Mon, Apr 19, 2010 at 5:54 PM, Ozgur Akgun <ozgurakgun at gmail.com<mailto:
>> ozgurakgun at gmail.com>> wrote:
>>
>>    Can you at least give an example of how you intend to use this "func"?
>>    Since you do not describe it's behaviour, it is very hard to make a
>>    useful
>>    comment (at least for me)
>>
>>    Best,
>>
>>    On 19 April 2010 16:54, Mujtaba Boori <mujtaba.boori at gmail.com
>>    <mailto:mujtaba.boori at gmail.com>> wrote:
>>     >
>>     > Hello
>>     > I am sorry for the silly question.
>>     >
>>     > I have a function as the following
>>     > func:: ((Float,Float) ->Bool) -> Float -> ((Float,Float) -> Bool)
>>     > I am trying to make calculation in this type ((Float,Float)
>>    ->Bool)  with Float and then pass the information to ((Float,Float)
>>    -> Bool)
>>     >
>>     > Thank again appreciated.
>>     > _______________________________________________
>>
>>     >
>>
>>
>>
>>    --
>>    Ozgur Akgun
>>
>>
>>
>>
>> --
>> Mujtaba Ali Alboori
>>
>>

--
Mujtaba Ali Alboori
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